Pneumococcal vaccine development initiative

Prevention of disease by vaccination is one of the approaches to control the high rates of morbidity and mortality due to this organism. A polyvalent polysaccharide vaccine has been available for several years but this vaccine is poorly immunogenic in infants and young children, who are at highest risk for invasive disease, and does not result in immunological memory. A 7-valent glycoprotein conjugate vaccine has recently been licensed for use in children in the United States. Several new 9- or 11-valent conjugate vaccines are undergoing trials. Other candidate vaccines using protein antigens that are common to all pneumococci, are also in different phases of testing. These vaccines, if efficacious, are likely to have an important role in reducing childhood mortality in developing countries. The WHO has an important role in promoting research to evaluate and planning strategies for introduction of these vaccines in developing country populations.

Current status of activities in pneumococcal vaccine development

The status of pneumococcal vaccines and the research and development needs were discussed and prioritized in a meeting in WHO in 1998 and updated in a meeting jointly organised by WHO and the GAVI Task Force on Research and Development in April 2001. These research priorities have been combined with other priority activities required for vaccine introduction and is being formulated into an Accelerated Development and Introduction Plan (ADIP). The plan targets at initiating the introduction of pneumococcal conjugate vaccines in Vaccine Fund eligible countries in 2006-7.

Meanwhile research to establish the value of pneumococcal vaccines are in progress. Studies are being initiated to measure the burden of pneumonia and pneumococcal disease in developing countries. Efficacy trials with 9 or 11-valent pneumococcal conjugate vaccines are in progress in South Africa, The Gambia and The Philippines. The South Africa trial is just completed and results are expected in May 2002. The other two trials are expected to be completed in 2005. Trials evaluating the safety and immunogenicity of maternal immunization, neonatal immunization and immunization of HIV-infected children are also ongoing.

A Radiology Working Group of Pneumococcal Vaccine Trialists, convened by WHO, has developed a standardised method to measure radiological pneumonia, which may be used to measure pneumonia burden and evaluate the impact of vaccination. A training and self-ssessment software has been developed for this purpose. Other standardization efforts include the development of standard procedures to study nasopharyngeal carriage of pneumococcus following vaccination and for estimating cost-effectiveness of pneumococcal vaccination.